■ ^ Agriculture
Research Direction generate
Branch de la recherche
Technical Bulletin 1987-2E
Sorghum and Sudangrass
on the Prairies
CODE 87/01/26 NO.
LIBRARY/BIBLIOTHEQUE OTTAWA K1A OC5
00 A g
The map on the cover has dots representing
Agriculture Canada research establishments.
Sorghum and Sudangrass
on the Prairies
Agriculture Canada Research Station
Agriculture Canada Research Station
Agriculture Canada Research Station
Lethbridge Research Station Contribution No. 10
Copies of this publication are available from:
Dr. D.J. Major
Plant Science Section
Research Branch, Agriculture Canada
Produced by Research Program Service
©Minister of Supply and Services Canada 1987
Cat. No. A54-8/1 987-2 F.
SORGHUM TYPES 2
GROWTH HABITS AND ADAPTATION 2
PRODUCTION PRACTICES 8
Weed Control 15
Crop Rotation 18
LITERATURE CITED 24
Grain sorghum ( Sorghum bicolor L.) was evaluated as a new crop on the
southern Prairies because of its reputation as a drought-tolerant crop.
Dates of seeding, row spacing, stand density, fertility, dates and
herbicide efficacy, diseases, methods of harvesting, and other agronomic
studies were conducted. Under dryland conditions, sorghum had no better
drought resistance than wheat and yields were not high enough to compete
with conventional cereals. A need for breeding early, higher-yielding
hybrids with resistance to seedling blight is indicated, and would
require a heavy resource commitment to a high risk research venture.
Sorghum- sudangrass (S_^ Sudanese [Piper Stapf.]) hybrids appear to have a
place as a dryland and irrigated forage crop on the southern Prairies.
Le sorgho grain ( Sorghum bicolor L.) a ete evalue comme culture
eventuelle dans le sud des Prairies en raison de sa reputation de
tolerance a la secheresse. On a conduit des essais sur les dates
de semis, 1 ■ ecartement des lignes, la densite de peuplement, la
fertilisation, les traitements herbicides, les maladies, les
methodes de recolte, ainsi que sur d'autres carac teres agronomiques .
En culture seche, le sorgho n'a pas demontre une meilleure resistance
a la secheresse que le ble et ses rendements n'ont pas ete assez
hauts pour lui permettre de faire concurrence aux cereales classiques.
On se trouve devant la necessite de selectionner des hybrides precoces,
plus productifs et possedant de la resistance a la brulure (fonte) des
semis et, par ailleurs, les ressources a engager dans les recherches
seraient considerables en regard des chances de succes. Les hybrides
sorgho-soudan (_S. sudanense (Piper Stapf.)), en revanche, semblent
offrir des possibilites pour cette region, tant en culture seche qu'en
regime i rr i gue .
Grain sorghum ( Sorghum bicolor L.) is a potential alternative to
traditionally grown cereal and forage crops in southern Alberta because
of its C4-dicarboxylic acid photosynthetic pathway, which is believed to
enhance adaptation to environments where water limits growth. Where
sorghum is commonly grown, practical experience indicates that sorghum
exhibits more drought resistance than most other crops (18).
This report represents the culmination of 15 years of research at
Lethbridge to assess the potential of sorghum in southern Alberta. It
began with the selection of early sorghums from CIMMYT and, ultimately,
early hybrids such as Pride P130 and Northrup King X8102. Studies were
conducted on row spacings and densities (6), growth analysis (11),
comparisons with other crops (7, 11), photoperiod responses (10), feeding
value (1, 2), the effect of chilling temperatures on sorghum growth (12)
and, most recently, the role of pathogens in stand establishment of
sorghum (4, 5).
Throughout these studies and in on- farm experiments in southern Alberta,
stand establishment has been a problem. This has also been alluded to in
many other studies. Ross and Webster (18) stated that the top 5-cm soil
temperature should be about 20°C before seeding. Gaudet and Major (5)
found that pathogenicity of seed-borne Pseudomonas and seed- and
soil-borne fungi is increased by exposure to low temperatures.
Consequently, the future of sorghum in the short-season regions
ultimately depends on the selection of sorghums resistant to seedling
blight ( Pseudomonas syrlngae ) . A concentrated breeding effort is
required to accomplish this.
The results of the current study indicate that, even when successfully
established, sorghum yields may not be high enough to compete economically
with wheat. The hope that sorghum would have higher drought resistance
than wheat has not been realized. Rather, the ability of sorghum to
thrive in arid conditions would appear to be related more to heat
tolerance than to drought resistance (16). A breeding program might also
be aimed at achieving a higher water- use efficiency.
Sorghum and sudangrass ( Sorghum sudanense [Piper Stapf]), close relatives
of corn and sugar cane, evolved in Ethiopia and the Sudan. They are
widely grown in the southern U.S. (Nebraska south to Texas), northeast
Africa, and India. Grain sorghums usually have dwarf genes associated
with them so they only grow about 1 meter tall, whereas forage sorghums
have no dwarf genes and grow to a height of about 2 meters. Three types
are used for forage: forage sorghum, sudangrass, and sorghum-sudangrass
hybrids. Forage sorghum has the highest dry matter yield under irrigation,
but sudangrass, and sorghum-sudangrass hybrids are better on dryland.
Initial research at Lethbridge was concentrated on dryland grain sorghum.
This was aimed at developing early maturing sorghum cultivars and hybrids,
a goal which was accomplished in less than 10 years.
GROWTH HABITS AND ADAPTATION
A major problem with sorghum production in southern Alberta is the poor
stand establishment that results from reduced germination, emergence, and
seedling growth at chilling temperatures. Sorghum requires a minimum
soil temperature of 8-10°C for germination, while the optimum temperature
is 24-28°C. The minimum temperature for seedling emergence is 10-12°C
but a dramatic increase in percentage emergence occurs at temperatures
above 20 °C.
In southern Alberta, soil temperatures after early seeding are generally
less than 15°C and, hence, limit germination and emergence. Consequently,
early seeding to make use of the whole growing season may not necessarily
be a good practice. Due to low soil temperatures, germination and
seedling emergence are delayed, thus increasing the risk of seed decay
and leaving the emerging seedling vulnerable to soil-borne disease.
Further, prolonged exposure to chilling temperatures can kill sorghum
seedlings. However, at locations in high latitudes such as Lethbridge,
delaying seeding to allow the soil to warm increases the risk of frost
In order to assess the effects of short-duration chilling temperatures,
an early maturing sorghum (Pride P130) was grown in a greenhouse with
day/night temperatures of 23/18°C and transferred to a controlled
environment chamber with day/night temperatures of 13/8°C for 3-, 7-, or
10 -day periods starting at seedling emergence and continuing to maturity
(12). Reductions in leaf number and plant height caused by chilling
temperatures were only temporary. Chilling temperature 28 days after
emergence caused tiller numbers to increase from three to as many as
eight per plant.
Most of the tillers appeared in a 14-day period starting about 10 days
after emergence (Fig. 1). Exposure to chilling temperature during the
short period when the plants were reaching maximum tiller number promoted
tillering. The maximum enhancement of tillering occurred at about day
28, when all of the tillers were visible in the control treatment.
Exposure to chilling temperatures caused the production of about two,
five, or four additional tillers for the 3-, 7-, and 10-day exposures.
This is consistent with previous reports that tillering response of
sorghum to chilling treatment is dependent on the plant's age.
To determine if above- freezing temperatures affected emergence, P130
sorghum and Pride 1108 corn were planted in sand and left for 3 days in
the greenhouse. The flats were exposed to 0.5°C, 5°C, or 10°C for
various lengths of time and then returned to the greenhouse. The
percentage of seedlings killed at the three temperatures indicated that
Pride 130 sorghum was much more sensitive to cold temperature exposure
than Pride 1108 corn. Figure 2 demonstrates how the percentage of seeds
that germinate increases from zero at about 4°C to 98% at 14°C and how
the time to germinate decreases from 7 days to less than 1 day. Other
experiments clarified the role of low temperatures on emergence. Low
temperatures per se are not a problem but they do reduce the vigour of
the sorghum seedling and its ability to resist soil- and seed-borne
pathogens. Thus, there was no physiological damage or chilling injury
due to low temperatures so reduced emergence was the result of a number
of factors such as inability to overcome soil impedence and to withstand
soil-borne pathogens and the infection of Pseudomonas syringae .
Grain sorghum is not currently recommended for Alberta but there have
been situations in which it has been produced. Sorghum is a coarse grain
with nutritional characteristics very similar to those of corn. However,
it generally does not command as high a price as does corn. The
consumption of grain corn is primarily in two distilleries (52 000
tonnes) and in feed manufacturing (18 000 tonnes). The sorghum used in
feed would likely be mainly in poultry feed. The grain used for
distilling is used for producing whiskey, gin, and vodka and for other
commercial alcohol uses.
Forage sorghum trials have been conducted at Lethbridge, Brandon, Morden,
and Ottawa since 1980. A summary of these trials indicated that forage
sorghums will provide a competitive alternative to the cereals for dryland
forage production on the southern Prairies (Table 1).
, . _< 15 193-0.853 doys)
I + e
10 20 30 40 50
DAYS FROM EMERGENCE
Fig. 1. Non-linear regression analysis of tiller number (excluding the
primary tiller) vs. days from seedling emergence and changes in tiller
number caused by the chilling temperature vs. days Erom seedling emergence
for Pride PI 30 soybeans.
• Pride PI30 - SORGHUM
o Pride 1108 - CORN
0°C (SORGHUM )
Fig. 2. The effect of length of exposure to various temperatures after
germination but prior to emergence on percentage of seedlings of Pride
P130 sorghum killed at 0, 5, and 10°C and of Pride 1108 corn killed at
Table 1. Average performance of selected forage sorghums (FS),
sorghum- sudangrass (SS) hybrids and sudangrass (SG) at Morden,
Brandon, Ottawa, and Lethbridge from 1978- 1984.
The combination of fall rye followed by sorghura-sudangrass is ideal for
double cropping where irrigation is available. The fall rye heads out in
late May and is ready to harvest for silage by the third week of June. This
is followed immediately by seeding sorghum- sudangrass, which is harvested in
late August or early September. Yields of double cropping have been similar
to yields of maize grown at Lethbridge (Table 2). There are still some
difficulties such as slow growth of sorghum immediately following the rye
harvest. Additional research is required to determine the cause of this.
Table 2. Component yield of various crops grown in double cropping
and of maize grown under irrigation at Lethbridge in 1984-86.
Prussic acid poisoning mainly occurs when livestock are fed green-chop
sorghum-sudangrass or are pastured on young sorghum or regrowth. It is
caused by dhurrin, a cyanogenic glucoside, which hydrolyzes to form the
respiratory poison, hydrogen cyanide, when ingested by animals. A 450-kg
cow will be killed by 1 gram of hydrogen cyanide, which could be present
in less than 2 kg of plant material. Most sudangrasses have been bred
for reduced levels of dhurrin but there are circumstances in which lethal
levels may still occur. Young regrowth, particularly after a killing
frost, is most dangerous. Nitrogen fertilization increases the levels of
dhurrin and levels can also increase when growth is slowed by injury,
moisture stress or cold temperatures. A New Zealand study (8) indicated
that irrigated crops contained 30-40% less prussic acid than those on
dryland. This difference would be magnified in southern Alberta because
of our extreme drought on dryland. In a crop containing lethal levels of
HCN, cattle will succumb within half an hour. Therefore, in potentially
dangerous situations, the feed should be analyzed before free access to
the crop is given. Where sorghum green- feed constitutes a major part of
the animals' diet, dietary supplementation with sulfur (1.2 g sulfur/g
HCN) will detoxify the feed (8). Cutting the crop for hay or silage will
result in disappearance of most or all of the dhurrin.
Sorghum- sudangrass hybrids will produce more dry matter than annual
cereals such as barley or oats. The crop should be seeded between 25 May
and 15 June. Seeding too early into cold soils can result in poor
emergence due to cool soil. Later seeding may not allow enough time for
the crop to make maximum growth before frost. The crop should be ready
for harvest in late August.
Seeds of sorghums of all types are susceptible to damage in adverse soil
conditions, particularly when the soil is cool. Therefore, seeding should
not begin until the day-time temperature of soil at 5- cm depth is about
20°C. As a rule of thumb, this will be after 25 May. In a date-of-planting
study conducted at Lethbridge, the percentage seeds established increased
as planting date was delayed after 15 May. However, yield decreased due to
later maturity of late-seeded sorghum. In practice, the most appropriate
course of action is to delay seeding. Therefore, a hybrid chosen for
seeding in late May must be capable of reaching maturity before fall frost.
To assess the effect of stand on yield, a seeding rate experiment was
conducted with P130 in 1980 and P145 in 1981 and 1982. Seeding rates
ranged from 5 to 90 kg/ha and the variables measured were stand
establishment (plants/m^) and yield. Population densities increased with
seeding rate but the percentage emergence was generally constant (Table 3).
The positive relationship between seeding rate and population density
decreased in 1982 compared with 1980 and 1981. This reduction may have
been due to increased interplant competition at the high seeding rates in
1982. There were essentially no differences in yield in spite of an
18-fold difference in population density. In 1981 and 1982, there were
slight reductions in yield at the 5, 10, and 90 kg/ha rates but not at
the 15 to 60 kg/ha rates. These results indicated that a seeding rate of
about 15 or 20 kg/ha should be suitable in short- season areas.
The relationship between the number of heat units and relative yield was
determined from data on the effect of seeding and harvest dates collected
at Lethbridge from 1978 to 1982 (13). For the hybrid in question, Pride
P145, 2400 corn heat units (CHU) were required to get maximum yield
(Fig. 3). Coincident with a reduction in yield was a reduction in test
weight. If the crop did not receive sufficient CHU to mature then the
seed was light and shrunken. Only the regions around Bow Island and
Medicine Hat would have sufficient CHU to allow seeding in late May and
still reach maturity. For dryland situations, sorghum- sudangrass hybrids
seeded in late May will have extracted most of the available soil
moisture by the end of August, in most years. Thus, the main criterion
for sorghum-sudangrass is not when grain maturity can be reached but how
long it takes the crop to extract all of the available moisture.
Table 3. The effect of seeding rate on final population density and
grain yield of P130 (1980) and P145 (1981 and 1982) sorghum grown
at Lethbridge, Alberta.
(plants/m 2 )
m 2 )
The critical factor in depth of seeding is to place the seed into
sufficient moisture for it to emerge before the soil dries out. If
seeded 2-3 cm deep in late May, sorghum will emerge in about 7 days. In
a depth-of-seeding experiment in 1982 we found that the optimum seeding
depth was about 4 cm. At shallower seeding depths, stand establishment
was reduced because of soil drying; at deeper seeding depths, poor
emergence and stresses introduced by late emergence reduced yield. If
the soil is too dry, deeper seeding will be necessary.
Disc drills are preferable to hoe drills in a double cropping system
because they appear to place the seed more gently into the soil than hoe
drills. Discers are generally not recommended for sorghum, but if they
must be used the seeding rate should be increased. To date, the biggest
problem has been providing a good seed bed immediately after the harvest
of the first crop. An irrigation followed by zero-till seeding into the
stubble will give the best results. Forage sorghum should be seeded at
15 kg/ha (about 15 lb/acre), sorghum sudangrass hybrids at 20 kg/ha and
- 10 -
RELATIVE YIELD = 0.936
( 11.4 - 0.00569C
1400 1600 1800 2000 2200 2400
CORN HEAT UNITS (CHU)
Fig. 3. The relationship between relative yield of sorghum and the
number of corn heat units accumulated between planting and harvest for
four planting and four harvest dates at Lethbridge in 1978-1982.
Table 4. Effect of row spacing on grain yield and grain yield components
of Pride X4004 and Pride X4053 sorghums in experiment 1 and 2, 1973
and in experiment 3, 1974.
a-c Within columns, within experiments, means followed by the same letter
do not differ at the P = 0.05 probability level using Duncan's multiple
sudangrass at 25 kg/ha using a row spacing of approximately 40 cm. For
most drills, it is desirable to plug or tape over the openings above every
other run to provide wider row spacings. If corn equipment is available,
seeding can be done in 75- cm (30") rows with no loss of yield.
Sorghum yields are not generally affected by row spacing. Three
experiments were conducted at Lethbridge in 1973 and 1974 to determine
the effect of row spacing and plant densities on sorghum yield (6).
The only effect of row spacing on grain yield was in experiment 1, which
resulted in higher grain yield for X4004 (Table 4). The yield component
results, however, indicated a differential response of the two hybrids
X4004 and X4053 to row spacing. As row spacing increased, panicles per
plant and panicles per square meter decreased for X4004 but yield per
panicle remained unchanged. The hybrid X4053, in contrast, had increased
yield per panicle as row spacing increased but panicles per plant and
panicles per square meter remained unchanged.
Increased population density had no consistent effect on grain yield in
experiments 1 and 3, but in experiment 2 yield increased as population
density increased (Table 5). Experiment 2 was on the driest of the three
sites. The plants established slowly and were always smaller than the
plants in the other experiments at comparable times during the season.
In all experiments, as population density increased, panicles per plant
decreased but panicles per square meter increased. Yield per panicle
decreased with increasing population density in experiments 1 and 3, but
there was no significant response in experiment 2.
Significant hybrid X population density interactions were detected for
panicles per plant and panicles per square meter in experiment 2. The
hybrid X4004 appeared to have a greater capacity to produce seed- bearing
tillers at low population densities. No significant interactions of row
spacing X population density were detected for yield or its components.
It was evident that tillering capacities of X4004 and X4053 were important
in stabilizing grain yields over a wide range of population densities.
On dryland, 75-cm wide rows will allow for some early season competition
within the row and conserve the moisture between the rows for late season
growth. These wide rows will also allow cultivation of the crop, which
has some value in weed control, allowing more uniform infiltration of
moisture and aeration of the soil. The disadvantage of wide rows comes
at harvest time since the stubble will not support a swath and a corn
head may be required for the forage harvester.
The seasonal pattern of sorghum whole plant dry weight accumulation,
studied at Lethbridge in 1976 and 1977, was similar for wheat and barley
but growth started later and continued later in the season (Fig. 4). In
1976, whole plant growth of barley and wheat levelled off about 1 Aug.
and, in 1977, about 15 July for barley and 15 Aug. for wheat (11).
Whole-plant growth of sorghum continued well into September in both years
but the increase was small after 15 Aug. in 1977. Sorghum grain yield
increased until 15 Sept. During the period 15 Aug. -15 Sept. of both
years, sorghum leaf, stem, and head dry weight decreased. Growth of
leaves and stems of barley maximized about 1 July in 1976 and 1977, and
only seed yield and whole- plant yield continued to increase. Wheat leaf,
stem, and head dry weights stayed the same or decreased after 15 Aug. and
15 July in 1976 and 1977, respectively, while seed dry weight continued
Whole-plant and grain growth rates were estimated during the linear phase
of growth (Fig. 4). Sorghum had significantly higher whole-plant growth
rate than wheat but not barley. Grain growth rate did not differ among
the three species in 1976 but barley grain growth rate was highest in
1977. In 1976, yields of barley and sorghum were similar because grain
growth rates and filling periods were similar. Wheat grain growth rate
and filling period tended to be lower than both barley and sorghum,
although not always significantly different. Nevertheless, the grain
yield of wheat was consistently lower.
Although sorghum matured 40 days later than either wheat or barley, its
effective whole-plant duration (58 days) was not significantly greater than
that of barley (50 days). The effective filling period duration was the
same (31 days) for the three species in 1976, but longer for sorghum (40
days) than for barley in 1977 (26 days). Barley had a higher daily grain
growth rate (150 kg/ha) than sorghum (109 kg/ha) in 1977, but, because of
a shorter filling period, grain yield was not significantly lower.
Sorghums are highly responsive to nitrogen if there is sufficient soil
moisture for crop growth as demonstrated by Hobbs and Krogman (7) at
Vauxhall. In a double- cropping situation, N should be applied in split
applications or with the irrigation system to minimize leaching. On
dryland, sorghum should be fertilized in the same manner as cereal
crops. For every metric tonne of dry matter per hectare there will be 15
kg of N and 6 kg of P2O5 removed from the crop. A 5.6 tonne/ha crop
of sorghum hay at 15% moisture translates to 70 kg of N/ha and 30 kg of
P20 5 /ha. For a double crop with a yield of 22 wet tons/ha of fall
rye and 27 wet tonne/ha of sorghum, nutrient uptake from the soil will be
200 kg N/ha and 80 kg P 2 5 /ha.
- 13 -
x -x-*-v x /
S.E. i i i I I I I III illli
I I I I I I I I ' I I 1 L_
I 15 I 15 I 15 I 15 28 I 15 I 15
J I I
15 I 15 27
Fig. 4. Seasonal changes in dry weight of plant components and standard
errors of whole plant dry weights for sorghum (x x) , wheat (o o) ,
and barley (• •) in 1976 and 1977.
Table 5. Effect of population density on grain yield and grain yield
components of Pride X4004 and Pride X4053 sorghum hybrids in
experiment 1 and 2, 1973 and in experiment 3, 1974.
2 . 98c
a-f Within columns, within experiments, means followed by the same
letter do not differ at the P = 0.05 probability level using
Duncan's mutiple range test.
- 15 -
Weed control studies to determine if conventional sorghum weed control
practices are effective in short-season areas have been conducted at the
Lethbridge Research Station. Atrazine is the most effective herbicide
but the persistent residue may be of concern. The most consistent weed
control is achieved by a fall application of atrazine at a rate of 1 kg
a.i./ha. Spring applications without incorporation with a double disc and
harrow have not always been successful because of the low, unpredictable
rainfall. Other effective herbicide treatments are bromoxynil plus MCPA
or 2,4-D up to the 6- leaf stage.
Two major weed problems are Russian thistle, which has some atrazine
resistance, and green foxtail. Green foxtail can be controlled in
rotation with cereals or by using a pre-plant incorporated treatment of
atrazine + raetolachlor and a seed safener.
Sorghum growing in short-season areas requires protection from weed
infestations for the entire summer as it does not provide enough ground
cover to provide competition against weeds even late in the year. The
development of early sorghum hybrids should allow delayed seeding to be
combined with a late cultivation to control late-emerging weeds. Weed
control problems in Alberta are similar to those described by Ross and
Webster (18) in Nebraska.
Weeds can be a problem on double cropping but usually both the winter and
summer crops, when adequately supplied with water and fertility, provide
ample competition to eliminate all weed growth. In some situations,
broadleaf weeds such as lamb's quarters and red-root pigweed are a
problem in the summer crop. On dryland, Russian thistle, in particular,
has been the primary problem.
If a commitment is made to sorghum production then atrazine provides the
best and cheapest form of weed control. This should be applied in the
fall at the rate of about 2 kg/ha in the first year and then lesser
amounts in subsequent years. One application of about 1 kg/ha of
atrazine is sufficient to control most weeds.
Atrazine appears to break down in southern Alberta soil at a rate of
about 75%/year depending on rainfall. Breakdown will occur when the soil
is moist but will be delayed in dry soil. An annual application of
atrazine at 1 kg/ha will result in a buildup in the soil so it should
only be applied the fall before seeding. An ideal rotation including
sorghum is a winter wheat/sorghum/fallow rotation. Atrazine is applied
after the winter wheat harvest at 1.5 kg/ha. This provides weed control
through the sorghum year and into the summerfallow year. At the time of
the sorghum harvest there will be about 0.4 kg/ha of atrazine and when
the winter wheat is seeded the following year there will be about 0.1
kg/ha of atrazine.
If atrazine is not used, then herbicides such as 2,4-D and Buctril M will
provide control of many broad leaf weed problems.
A study conducted to assess the factors influencing seedling emergence
(5) showed that the type of soil and seed source affected seedling
emergence. Autoclaving the soil to kill soil-borne organisms resulted
in higher emergence at 15/5°C regime (Table 6) compared with unautoclaved
soil. Cornell mix, which is a greenhouse mixture of equal parts of
sand, peat, and vermiculite, was very porous and caused less impedance
to the seedling than did soil. In this study, two soil-borne organisms,
F usarium tricinctum and F_^ oxysporum , were used to inoculate soil
planted to disease-free seed. It was clear from these results that the
capacity of soil-borne fungi to infect sorghum seedlings was enhanced at
low temperatures. This explains why only about 30% of the seed emerges
when the crop is seeded in early May and about 90% emerges when it is
seeded in early June. Another pathogen infects the flower at heading
time and it may also be involved in reduced seed set, shrivelled seeds
and low test weight. Infected seed will also exhibit reduced vigour and
lead to poor emergence of the following crop.
Table 6. The combined percent emergence of three sorghum
cultivars grown in two autoclaved rooting media at 30/20°C
and 15/5°C day/night temperatures when inoculated with
Fusarium oxysporum and F. t ricinctum .
Cornell mix 94a 70a
Lethbridge loam soil 78b 40b
Check 90a 82a
F. oxysporum (No. 1) 93a 46bc
F. oxysporum (No. 2) 79a 57b
F. tricinctum 82a 35c
a-c Means within columns and within treatments followed by
the same letter did not differ at the P = 0.05 probability
level using Duncan's Multiple Range Test.
- 17 -
Table 7. Percentage germination, root and shoot length, percentage
discoloration, and incidence of P^ s^ syrlngae in surface-sterilized
and unsterilized sor
% of seedlings with
'SS = surface sterilized, US = unsterilized.
+A seed was considered germinated if extension of the coleoptile and/or
coleorhiza was observed.
s Means within lots significantly different at *, P = 0.05 and **, P = 0.01
using analysis of variance.
Cleans within lots significantly different at +, P = 0.05 and +f, P = 0.01
using chi- square test for homogeneity.
*n.d. = no data
- 18 -
A seed-born bacterium, Pseudomonas syringae pv. syringae ( P. s. syringae ) ,
was identified as a cause of stunting and discoloration of the roots and
coleoptiles of sorghum seedlings (4). The incidence of P^ s_^ syringae in
nine lots of field-grown sorghum seed (Table 7), produced in 3 different
years in southern Alberta, varied from 8 to 67% (average = 38%). Surface
sterilization of seed with 10% sodium hypochlorite reduced stunting and
necrosis of root and shoot tissues from hand-harvested, but not from
mechanically harvested, seedlots. This indicated that the bacteria were
internally borne within the seed of mechanically harvested seeds and on
the surface of hand-harvested seedlots. Internal infection of the seed
by P^ s^ syringae may be promoted by mechanical damage to the seed which
occurs during harvesting. Sorghum seedlings from seed inoculated with
strains of P^ s^ syringae developed stunted and discolored roots and
coleoptiles when placed on moist filter paper and yielded fewer emerged
seedlings than uninoculated controls when sown in autoclaved or untreated
field soil in a growth chamber. Strains of the pathogen differed
markedly in the severity of symptoms produced in sorghum seedlings.
However, there is still a problem with disease. Due to its susceptibility
to cold temperatures, sorghum can be infected by soil- and seed-borne
pathogens that seriously reduce emergence.
Agriculture in the nonirrigated areas of southern Alberta is primarily
limited to cereal production because of low precipitation (400 ram per
year) and a short growing season length (117 frost-free days). This
virtual monoculture production system results in excessive reliance on
summer fallowing, overdependence on economic returns from single crops,
and reduced opportunity for weed and pest control. Consequently, the
introduction of new crops and diversification of cropping systems would
potentially provide both economic and agronomic benefits to southern
Thus, while the potential to develop sorghum hybrids to reach maturity in
southern Alberta has been demonstrated (10) and many of the production
practices such as dates of seeding, rates of seeding, and row spacing have
been defined (6, 13), the agronomic and economic feasibility of sorghum
production as an integral part of dryland agriculture in the southern
Canadian Prairies has not been adequately considered. Therefore an
intensive long-term rotation experiment was conducted from 1978 to 1984,
to determine the response of sorghum in rotation with other crops grown
in southern Alberta (9).
Sorghum yields ranged from 1161 to 2474 kg/ha in the various rotations
averaged over the 5-year period (Table 8). Highest yields were observed
when sorghum followed fallow in the rotation, regardless of rotation
length. Significantly lower sorghum yields were observed in 3-year
rotations where sorghum followed spring or winter wheat. Still lower
- 19 -
yields were observed when sorghum succeeded sorghum and lowest yields
occurred when sorghum followed barley in the rotation. The high yields
observed after fallow were probably almost entirely attributable to
greater availability of moisture. The relatively good performance of
sorghum after winter wheat may be partially the result of a disease
outbreak in the winter wheat during 1981 which required plowing down of
the winter wheat in midseason and resulted in a partial fallow period
prior to sorghum establishment. The relatively low yields observed in
the continuous sorghum and sorghum-barley rotations were attributed to
increased infestation of weeds such as Russian thistle and kochia. On
average, the ratio of yield on stubble to yield on fallow was 0.63 for
sorghum and 0.69 for spring wheat. The number of crops preceding the
fallow year had no effect on sorghum yield after fallow as is evident in
the comparable sorghum yield for rotations S-SW-F and S-F (Table 9).
Table 8. Effect of the preceding crop on the yield of
sorghum in a study comparing six sorghum rotations
grown at the Lethbridge Research Station (1978-1984).
Rotationt Preceding crop (kg/ha)
S-SW-F Fallow 2474a
S-F Fallow 2415a
S-F-WW Winter wheat 1849b
S-F-SW Spring wheat 1712b
S Sorghum 1466c
S-B Barley 1161d
•S = sorghum, SW = spring wheat, F = fallow, WW = winter
wheat, B = barley.
+Yield values followed by the same letter are not
significantly different at P = 0.05 based on calculated LSD.
Highest overall rotation yields were obtained for the continuous cropping
rotations, the sorghum- bar ley rotation, and the continuous sorghum
rotations. The lowest total yield was obtained for the sorghum- fallow
rotation (Table 9). The 30-year mean total precipitation at Lethbridge
was 405 mm and all but one of the years of this study had crop year
precipitation that was at least 75% of average. Thus, it is probable
that over a 100-year period there would be years with considerably less
precipitation than was encountered in this study. Also, the region of
southern Alberta which would be most likely to produce sorghum receives
even less precipitation than does Lethbridge. Therefore, it would not be
prudent to recommend continuous cropping throughout southern Alberta
based on the results of our research.
- 20 -
Table 9. Yields in a study comparing six sorghum
rotations grown at the Lethbridge Research Station
( kg/ha )+
'Yield values followed by the same letter are not
significantly different at P = 0.05 based on calculated
Mean rotation yields ranged from 577 kg/ha in 1984 to 1968 kg/ha in 1980,
probably reflecting differences in levels of available soil moisture. The
differences attributable to variability in precipitation were greater than
any differences detected among the rotations. This emphasizes the critical
role played by rainfall in the dryland agriculture of southern Alberta.
The major limitation to crop production in southern Alberta is the
availability of moisture. Between 44 and 79% of the variability in yields
of sorghum and wheat in this study was accounted for by differences in
growing season precipitation and the relationship was strongest in stubble
crops, where moisture deficits were most severe. The effect of moisture
on yield was best demonstrated in the relationship between yield and total
available moisture levels (Fig. 5), defined as available spring soil
moisture plus growing season precipitation. For wheat fallow, total
- 21 -
available moisture accounted for 97% of the variability in yield. The
regression coefficients for the relationship between yield and total
available moisture were similar for sorghum (1.30 kg/m 3 ) and for wheat
(1.35 kg/m 3 ) when seeded on fallow. The regression coefficients were
also similar to each other but lower when seeded on stubble: 1.11 and
1.12 kg/m 3 , for sorghum and wheat, respectively. The X-intercept of
the relationship represented the minimum available moisture required to
produce sorghum yields. The values obtained were 95 and 102 ra 3 /ha for
sorghum on stubble and fallow, respectively. The corresponding values
for spring wheat were 85 and 124 m 3 /ha, respectively. Based on these
estimates, there was no evidence that sorghum possessed an advantage in
drought resistance or water-use efficiency over wheat under southern
Alberta conditions. While our estimates of total available moisture may
not have been an accurate estimate of total evapotranspiration, our
water-use efficiencies were reasonably close to those published by Porter
et al. (17), Olson (15), Garrity et al. (3) and Stewart et al. (19). Our
values were within the range of values that Garrity et al. (3) obtained
for a crop that used about 300 mm of water. They found that water-use
efficiency increased as total evapotranspiration increased. This would
be the case when comparing our fallow with stubble conditions. The
values that Neild (14) obtained were somewhat higher than our 2 kg/m 3
but he obtained his estimate for sorghum grown in a higher rainfall
region than occurs in southern Alberta. The relationship that Stewart et
al. (19) obtained was very much like the one obtained in this study.
Theirs had an X-intercept of 143 m 3 /ha as minimum evapotranspiration
for crop production.
The results of this study demonstrated that consistent production of
early maturing grain sorghum was possible under southern Alberta
conditions and that yields corresponded closely to those of spring wheat.
The yield of sorghum in rotation was similar to that of wheat; sorghum
yields on stubble were 63% of those on fallow compared with 69% for
wheat. From an economic standpoint, a 3-year rotation including sorghum
in the first year, spring wheat or winter wheat in the second year, and
fallow in the third year is likely to be most desirable. Because of the
low price of sorghum relative to that of wheat, however, economic returns
from rotations including sorghum would likely be considerably lower than
from conventional spring wheat or winter wheat rotations. As well, its
inconsistent stand establishment in spring predisposes sorghum to weed
and disease infestations so that agronomic management requirements for
sorghum are more intensive than those of traditional cereals.
Consequently, the inclusion of sorghum in crop rotations in southern
Alberta cannot currently be recommended until the problems of stand
establishment and low yield have been overcome.
100 200 300 400
Available water (mm)
Fig. 5. Relationship between yield and total available water (soil
moisture + growing season precipitation) for sorghum and spring wheat
grown on fallow and stubble from 19781984. (R 2 for the relationships
in the order in which they appear in the legend: 0.78, 0.64, 0.97, 0.84)
The forage sorghums have the coarsest stems and the sudangrasses have the
finest stems. Thus the sudangrasses are the easiest to harvest for hay
as they will dry in the swath more rapidly. They are also more suitable
for grazing. There is seldom sufficient moisture available for regrowth
in southern Alberta so the harvest date should be dependent on the time
when growth ceases so that yield is maximized. Sorghum-sudangrass hybrids
grown on irrigation will have a high moisture content and it may not be
possible to dry the swath. Irrigated sorghum should probably be preserved
Grain sorghum should be direct -combined with the cutter bar raised so
that only the heads enter the combine. If a frost has not killed the
stems they will remain green even when the grain is mature so it is
important to minimize the amount of tissue entering the combine. The
ideal moisture content for combining grain sorghum in southern Alberta is
between 18 and 25%. If the crop is allowed to dry to 14% or less, some
stalk breakage may occur and yield will be reduced. If the crop is
harvested at moistures greater than 14%, aeration or drying will be
necessary. The cylinder speed has to be carefully adjusted so that the
hulls are removed from the seed.
- 24 -
1. Gardiner, E. E., Dubetz, S. and Major, D. J. 1981. Sorghum, wheat
and corn in diets for broiler chicks. Can. J. Anim. Sci. 61:
2. Gardiner, E. E., Major, D. J. and Dubetz, S. 1982. Substitution of
sorghum for wheat in diets for laying hens. Can. J. Anim. Sci. 62:
3. Garrity, D. P., Watts, D. G. c, Sullivan, Y. and Gilley, J. R.
1982. Moisture deficits and grain sorghum performance:
evapotranspirat ion-yield relationships. Agron. J. 74: 815-820.
4. Gaudet, D. A. and Kokko, E. G. 1986. Seedling disease of sorghum
grown in southern Alberta caused by seed-borne Pseudomonas syringae
pv. syringae . Can. J. Plant Path. 8: (in press).
5. Gaudet, D. A., and Major, D. J. 1986. Factors affecting seedling
emergence of sorghum for short-season areas. Plant Dis. 70: 572-575.
6. Hegde, B. R., Major, D. J., Wilson, D. B. and Krogman, K. K. 1976.
Effects of row spacing and population density on grain sorghum
production in southern Alberta. Can. J. Plant Sci. 56: 31-37.
7. Hobbs, E. H. and Krogman, K. K. 1981. Sorghum and barley in
southern Alberta: Grain yield response to irrigation and
fertilizer. Can. J. Plant Sci. 61: 837-842.
8. Hunt, B. J. and Taylor, A. O. 1976. Hydrogen cyanide production of
field- grown sorghums. N. Z. J. of Exper. Agric. 4: 191-194.
9. Janzen, H. H., Major, D. J. and Lindwall, C. W. 1987. Comparison
of crop rotations for sorghum production in southern Alberta. Can.
J. Plant Sci. (in press).
10. Major, D. J. 1980. Photoperiod response characteristics
controlling flowering of nine crop species. Can. J. Plant Sci. 60:
11. Major, D. J. and Haraman, W. M. 1981. Comparison of sorghum with
wheat and barley grown on dryland. Can. J. Plant Sci. 61: 37-43.
12. Major, D. J., Hamman, W. M. and Rood, S. B. 1982. Effects of
short -duration chilling temperature exposure on growth and
development of sorghum. Field Crops Res. 5: 129- 136.
13. Major, D. J. and Wilson, D. B. 1982. Sorghum production in dryland
short-season conditions. Proc. 37 Annu. Corn and Sorghum Ind. Res.
Conf. 37: 10-25.
- 25 -
14. Neild, R. E. 1982. Temperature and rainfall influences on the
phenology and yield of grain sorghum and maize: a comparison.
Agric. Meteorol. 27: 79-88.
15. Olson, T. C. 1971. Yield and water use by different populations of
dryland corn, grain sorghum, and forage sorghum in the western corn
belt. Agron. J. 63: 104-106.
16. Peacock, J. M. and Heinrich, G. M. 1984. Light and temperature
responses of sorghum. Pp. 143-158 in Agrometeorol. of Sorghum and
Millet in the semi-arid tropics. S. M. Virmani and M. V. K.
Sivakuraar, eds. Proc. Int. Symp. 15-20 Nov 1982, ICRISAT Center,
India. Patancheru, India.
17. Porter, K. B., Jensen, M. E. and Sletten, W. H. 1960. The effect
of row spacing, fertilizer and planting rate on the yield and water
use of irrigated grain sorghum. Agron. J. 52: 431-434.
18. Ross, W. M. and Webster, O. J. 1970. Culture and use of grain
sorghum. USDA/ARS Agric. Handbook No. 385.
19. Stewart, B. A., Musick, J. T. and Dusek, D. A. 1983. Yield and
water use efficiency of grain sorghum in a limited
irrigation-dryland farming system. Agron. J. 75: 629-634.
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